Cable tray or cable duct systems that can be walked on are deployed, e.g., in order to link supply chains of individual elements of industrial plants, in particular to advance electric lines to machines or robots, as schematically shown in FIG. 1. For this purpose, cable duct systems of different dimensions are used, which are usually installed on site. In order to advance the cable ducts to the required positions, it is often required to cut the cable duct systems and to provide branch ducts, as schematically shown in FIG. 1.
One demand which is frequently made to cable duct systems is that these systems have to be able to be walked on by people. For safety reasons, it is thus necessary to configure the cable duct systems such that they comprise sufficient slip resistance in order for a person treading on the cable duct not to slip. For this purpose, a lid with a ribbing on its upper surface is commonly used, said lid being put on the cable duct tray. There are different options for mounting the lid onto the cable duct tray, for instance, latching systems with which the lid latches directly onto the cable duct tray. Spring members and/or clamps by means of which the lid is mounted onto a cable duct tray are also used. Moreover, the use of turn locks or quarter-turn locks which are mounted onto the lid and with the help of which the lid is locked onto the cable duct tray is also well-known.
In the prior art, e.g., a lid for cable duct systems that can be walked on is known, said lid being formed from a curved steel sheet with an aluminum checker sheet riveted onto its upper surface. Quarter-turn locks are commonly used for fixing said lid. In order to mount the quarter-turn locks onto the duct lid, however, it is necessary to provide mounting holes in the lid. For this purpose, a specific step drill is used by means of which a through hole is drilled through the aluminum checker sheet and the steel lid, wherein the aluminum checker sheet is cut in the mounting area by way of the steps of the drill. Such a cable tray system that can be walked on is shown, e.g., in the catalog for cable tray systems that can be walked on published by the company Niedax GmbH & Co. KG.
Furthermore, U-shaped, structured metal lids are well-known, in particular checker sheet lids made of aluminum and steel. Said lids are provided with a ribbing along their whole outer surfaces, i.e., at the lateral parts and the upper surface.